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way service must be marked with the maximum current which they can safely carry for 30 minutes, starting cold.
i. Terminal blocks, when used on motors, must be made of approved non-combustible, non-absorptive insulating material, such as slate, marble or porcelain.
j: Adjustable-speed motors, unless of special and appropriate design, if controlled by means of field regulation, must be so arranged and connected that they cannot be started under weakened field.
k. The use of soft rubber bushings to protect the lead wires coming through the frame of motors is permitted, except when installed where oils, grease, oily vapors or other substances known to have rapid deleterious effect on rubber are present in such quantities and in such proximity to motors as may cause such bushings to be liable to rapid destruction. In such cases hardwood properly filled, or preferably porcelain or micanite bushings, must be used.
$ 209. Railway power plants.-a. Each feed wire before it leaves the power plant must be protected by an approved automatic circuit-breaker, or other device, which will immediately cut off the current in case of an accidental ground. This device must be
mounted on a fireproof base, and in full view and reach of the attendant.
$ 210. Storage or primary batteries.-a. When current for light and power is taken from primary or secondary batteries, the same general regulations must be observed as apply to similar apparatus fed from generators developing the same difference of potential.
b. Storage battery rooms must be thoroughly ventilated. c. Special attention is directed to the rules for wiring in rooms where acid fumes exist (see § 426, i, j, of this chapter).
d. All secondary batteries must be mounted on non-absorptive, non-combustible insulators, such as glass or thoroughly vitrified and glazed porcelain,
e. The use of any metal liable to corrosion must be avoided in cell connections of secondary batteries.
8 211. Transformers.-a. In central or sub-stations the transformers must be so placed that smoke from the burning out of the coils or the boiling over of the oil (where oil-filled cases are used) can do no harm.
b. In central or sub-stations casings of all transformers must be permanently and effectively grounded.
The cases or frames of transformers used exclusively to supply current to switchboard instruments must be grounded, unless they are installed and guarded in all respects as required for the higher voltage circuit connected to them.
(As amended by ord. effective May 29, 1919) Sec. 312. Wires on outside of buildings.
8 313. Services.
§ 314. Transformers.
Sec. 312. Wires on outside of buildings.-a. This article shall not apply to conductors on highways.
b. Wires must, for services of No. 6 B. & S. gauge or smaller, consist of approved rubber covered multiple conductor cable and must enter the building in the manner prescribed by the second paragraph of § 312f of this chapter. At the first point of attachment to building frame multiple conductor cables must either be secured to strain insulators spaced not less than one foot from any adjacent woodwork and in turn secured to petticoat or strain insulators or the conductor must be separately attached to petticoat insulators spaced not less than 6 inches apart. If necessary to carry the service cable upon
the face of the building before entering, it may be extended in flexible metal conduit, or a waterproof conduit system must be employed.
c. Wires must be at least 8 feet above the highest point of roofs over which they pass or to which they are attached and roof structures must be substantially constructed. Wherever feasible, wires crossing buildings must be supported on poles independent of the buildings. Roof lines will be permitted only under special authorization in writing.
d. Wires extended on the exterior walls of buildings must have a rubber insulating covering, and, if not protected by fuses, must be kept at least 1 foot apart and supported on petticoat insulators of glass or porcelain placed not more than 15 feet apart, the distance between supports to be shortened if wires are liable to be disturbed.
e. Wires must be so spliced or joined as to be both mechanically and electrically secure without solder. The joints must then be soldered, to insure preservation, and covered with an insulation equal to that on the conductors.
All joints must be soldered unless made with some form of approved splicing device.
f. Wires must, where they enter buildings, have drip loops outside, and the holes through which the conductors pass must be bushed with non-combustible, non-absorptive insulating tubes, slanting upward toward the inside; or the service wires may be brought into buildings through a single iron conduit, in which case the conduit shall be equipped with an approved service-head. The inner end must extend to the service cut-out, and if a cabinet is required by this chapter must properly enter the cabinet.
Metal conduits, containing service wires must be insulated from the metal conduit, metal moulding, or armored cable system within the building and all metal work on or in the building or they must have the metal of the conduit permanently and effectually grounded to water piping, gas piping or other suitable grounds, provided that when connections are made to gas piping, they must on the street side of the meter. This ground connection to be independent of and in addition to any other ground wire on metal conduit, metal moulding or armored cable systems within the building.
$ 313. Services.-a. Each building shall be supplied by a separate service.
b. Where a row of separate buildings is to receive its supply from an overhead main, one service cable shall be run from the pole to the row, and from the first attachment to the building sub-services or a service main shall extend in conduit along the face of the row. One service cable shall supply not more than five buildings, except under special permission in writing, given in advance.
The same plan of sub-services may be employed in connection with underground services, under the same restrictions.
$ 314. Transformers.-a. Transformers 'must not be attached to any building when the potential exceeds 550 volts, except by special permission and when attached to buildings must be separated therefrom by substantial supports.
§ 315. Grounding low potential circuits.-a. Direct-current threewire systems. Neutral wire must (except where supplied from private industrial power or lighting plants where the voltage does not exceed 550 volts) be grounded and the following rules must be complied with:
1. The neutral wire must be permanently and effectively grounded at the central station. The ground connection must include all available underground complete metallic piping systems.
2. In underground systems the neutral wire must also be grounded at each distributing box through the box or on the individual service as provided in paragraphs c to g, inclusive, of this section.
3. In overhead systems the neutral wire must be grounded every 500 feet, as provided in paragraphs c to g of this section.
b. Alternating-current secondary systems. Transformer secondaries of distributing systems (except where supplied from private industrial power or lighting plants where the primary voltage does not exceed 550 volts) must be grounded, provided the maximum difference of potential between the grounded point and any other point in the circuit does not exceed 320 volts. The following rules must be complied with:
1. The grounding must be made at the neutral point or wire, whenever a neutral point or wire is accessible.
2. When no neutral point or wire is accessible, one side of the secondary circuit must be grounded.
3. The ground connection must be at the transformers or on the individual service, as provided in paragraphs c to g of this section, and when transformers feed systems with a neutral wire, the neutral wire must also be grounded at least every 500 feet.
c. Ground wire, in buildings. When the ground connection is inside of any building, or the ground wire is inside of or attached to any building (except central or sub-stations) the ground wire must be of copper and have an approved rubber insulating covering, National Electrical Code Standard, rom 0 to 600 volts.
d. Ground wire, sizes. The ground wire in direct-current threewire systems must not at central stations be smaller than the neutral wire and not smaller than No. 6 B. & S. gage elsewhere. The ground wire in alternating current systems must never be less than No. 6 B. & S. gage.
On three-phase systems the ground wire must have a carrying capacity equal to that of any one of the three mains.
e. Ground wire, installation. The ground wire must, except for central stations and transformer sub-stations, be kept outside of buildings as far as practicable, but may be directly attached to the building or pole by cleats or straps or on porcelain knobs. Staples must never be used. The wire must be carried in as nearly a straight line as practicable, avoiding kinks, coils and sharp bends, and must be protected when exposed to mechanical injury.
f. Ground connections, central stations. The ground connections for central stations, transformer sub-stations, and banks of transformers must be permanent and effective and must include all available underground piping systems, including the lead sheaths of underground cables.
g. Ground connections, generally. For individual transformers and building services the ground connection may be made as in paragraph f of this section, or may be made to water piping systems running into buildings.
With overhead service, this connection may be made by carrying the ground wire into the cellar and connecting on the street side of meters, main cocks, etc.
Where the service enters the cellar or basement, this connection may be made by carrying the ground wire through the cellar or basement and connecting as above.
Where the ground wire is run through any part of a building, unless run in approved conduit, it shall be protected by porcelain bushings through walls or partitions and shall be run in approved moulding, except that in basements it may be supported on porcelain.
Connections should not be made to piping systems which have cement joints, but should only be made to complete metallic pipe systems.
(As amended by ord. effective May 29, 1916) Sec. 416. Wires, general.
§ 417. Underground conductors.
420. Limitation of potential.
424. Switches. 425. Electric heaters. 426. Wires, low potential systems. 427. Armored cables. 428. Interior conduits. 429. Metal mouldings.
447. Wires, extra-high potential. Sec. 416. Wires, general.-a. Wires must not be of smaller size than No. 14 B. & S. gage, except as allowed for fixture work and pendant cord.
b. Conductors of size No. 8 B. & S. gage or over used in connection with solid knobs must be securely tied thereto. If wires are used for tying they must have an insulation of the same type as the conductors they confine. Split knobs or cleats must be used for the support of conductors smaller than No. 8 B. & S. gage.
Knobs or cleats which are arranged to grip the wire must be fastened by either screws or nails. If nails are used, they must be long enough to penetrate the woodwork not less than 12 the length of the knob and fully the thickness of the cleat, and must be provided with washers which will prevent, under reasonable usage, injury to the knobs or cleats.
c. Wires must be so spliced or joined as to be both mechanically and electrically secure without solder. The joints must then be soldered unless made with some form of approved splicing device, and covered with an insulation equal to that on the conductors.
Stranded wires (except in flexible cords) must be soldered before being fastened under clamps or binding screws, and whether stranded or solid, when they have a conductivity greater than that of No. 8 B. & S. gage they must be soldered into lugs for all terminal connections, except where an approved solderless terminal connector is used.
d. Wires must be separated from contact with walls, floors, timbers or partitions through which they may pass by non-combustible, non-absorptive insulating tubes, such as glass or porcelain, except at outlets where approved flexible tubing is required.
Bushings must be long enough to bush the entire length of the hole in one continuous piece, or else the hole must first be bushed by a continuous waterproof tube. This tube may be a conductor, such as iron pipe, but in that case an insulating bushing must be pushed into each end of it, extending far enough to keep the wire absolutely out of contact with the pipe.
e. Where not enclosed in approved conduit, moulding or armored